Heat exchanger



J. H. ROHRER- HEAT EXCHANGER Feb. 7, 1939,

Filed Feb. 4, 1957 r Inventor: Jo'slbhflkokrer;

.9 LTMM Q Patented reb.1,;19'f39 j UNI-TED, s rArEs PAT-Eur oFI-ucs2.146.352 m'r momen Josiah 11.1mm, Philadelphia, Pa., smiof one-half toDay and Zimmermann, Incorporated..

Marylan Philadelphia, Pa, a corporation of Application February 4, 1931,Serial is. 12am V 2 claim. (01. 257-262) a 1 I This invention relates toheat exchangers and more particularly to a tube construction which maybe readily assembled in accordance with the area of the exterior surfaceavailable for contact A with the hot gases passing thereover. In thestructures of this type the tube and the fins mounted thereon usuallyhave different coefficients of expansion and, upon heating, small spacesdevelop between the interior surfaces of the fin blocks and the adjacentexterior surface of the tubes on which they were mounted. These spacesreduce very sharply the efiicacy of the heat transfer from the gasespassing over the exterior surfaces of the fin blocks to the fluid in theinterior of the tubes. In addition to this objection-the heat exchangersof this type are,

also objectionable because the assembly of the unit can not beaccomplished without the dimculties arising from the necessity for.shrinking I 7 these are wholly unsuitable with the high pressures andtemperatures employed in-the econ-- omizers for modern steam generatingplants.

The sheet metal constructions also usually have spaces in theinteriorinwhichboiler scale may collect, with resultant decrease of heattransfer, and inaddition, the fluid carrying interior space, by reasonof its construction, cannot be cleaned. v

with heat exchangers or economizers of the types heretofore availablealso, the structure could not readily be assembled in its entirety at Ithe place of installation, but must be assembled, f shipped to the placeof use and thus subjected to possible injury. It is an object ofobjectionable features heretofore encountered.

It is also an objectfiof the present invention to provide an economizerwhich may be readily assembled from unit parts and in desired siau.

the present invention to providea tube construction forheat exchangersor economizers which'overcomes the difficulties and It is also an objectof the present invention to provide a heat exchanger or economizer whichis simple in construction, and which has a large heat transfer surfaceon the exterior and a suitable heat transfer surface in the interiorthereof with the outer surface shaped to effect substantially uniformheat transfer to the inner surface.

It is a further object of the present invention I Y to provide aneconomizer composed of a plurality of units and preferably unit forgingswhich may be quickly and easily assembled by welding.

It is a further object of the present invention to provide a heatexchanger or economizer which may be assembled in accordance with theheat transfer requirements.

It is a further object of the present invention J to provide aneconomizer which will be satis-- factory at high pressures andtemperatures.

It is a further object of the present invention to provide a heatexchanger or economizer having exposed surfaces which are particularlyadapted to receive a coating or covering forregulating and controllingthe heat transfer characteristics.

Other objects of the invention will appear from the annexedspecification and claims.

The nature and characteristic features of the invention will be morereadily understood from the following description, taken in connectionwith the accompanying drawing forming part hereof, in which:

Figure 1 is a'front elevational view of an economizer or heat exchangerassembly embodying the .main features of the present invention;

Fig. 2 is a vertical central sectional view of a heat exchanger unitforging prior to assembly, illustrating certain details of construction;

Fig. 3 is ahead elevational view of a preferred form of heat exchangerunit which may be employed in the heat exchanger assembly;

Fig. 4 is an end elevational view of a modified form ofheat exchangerunit which may be employed in the heat exchanger assembly;

. Fig. 5 is an end elevational view of a further modified form of heatexchanger unit which may be employed in the heat exchanger assembly; and

lustrative m 1 y. and that various modifications a Fig. 61s a.fragmenary view partly in elevation urse, be understood that the deandchanges may be made in the structure disclosed without departing fromthe spirit of the invention.

Referring more particularly to Fig. 1 of the drawing, it will be seenthat the preferred assembled form of the heat exchanger or economizer ofthe present invention includes a plurality of headers Ill, a pluralityof connecting tubes H, a plurality of heat exchange units l2 and aplurality of return bends IS.

The headers It) may be of any desired construction with suitable spacein the interior thereof for the passage within the header III of thefluid to be heated, and may be of metal withplugs i4 threaded thereinopposite the connecting tubes II.

The connecting tubes ll may also be of any preferred construction, andthese connecting tubes are secured in any preferred manner to theheaders III.

The heat exchange units I2, which are of particular importance inconnection with the present invention, may be made in a number ofdifferent shapes but are each constructed in one piece as forgings orotherwise weldable units. The assembly may include units I! all of thesame external shape or may include units of different external shapes,as hereinafter more fully referred to.

The preferred form of heat exchanger unit forging is illustrated indetail in Figs. 2 and 3, and includes an inner cylindrical surface I!for direct contact in the assembly with the liquid to be heated. I

The unit forging If as illustrated in Fig. 2 is provided at theextremities of the inner surface II with chamfered portions IQ forwelding. This unit forging I2 is accordingly suitable for use as anintermediate unit of the assembly by being arranged in co-axialrelationship with other and similar unit forgings and with the innersurfaces II in alinement. 4

The unit forging I2 is also suitable as an end unit of a seriesterminating adjacent a header in for connection to one of the connectingtubes ll, or as the other end unit of a series of units terminating atone of the return bends I! for connection thereto.

The chamfered portions i8 permit of welding the units together end toend in any desired manner but are particularly suitable for flashwelding in the assembling of the heat exchanger at the place ofinstallation from headers l0. return bends I3 and unit forgings II.

The heat exchange unit I! is constructed, as referred to above, as aforging of a single body of metal and is preferably provided with aportion I! extending outwardly and generally perpendicular to the end toend axis of the unit to provide a fin, flange or rib. This flangedportion I! has the surfaces thereof which face toward the ends of theunit I! preferably shaped substantially in accordance with the uniformheat transfer characteristic curve of the forged metal.

The portions of the surface of the flange il, indicated at ll, which arerelatively close to the interior surface ll, extend substantially towardeach other and represent the flatter portion of the curve, while theportions of the surface of the,

shaping of the surfaces of the flange l1 provides for a substantiallyequal distribution of the heat absorbed at the exterior surface of theflange l1, and including surfaces l8 and i3, and passing through thewalls of the unit to the interior surface i5, so that a substantiallyuniform temperature prevails along the interior surface [5 of the uniti2.

The heat exchanger unit i2 is also preferably shaped in end elevation asillustrated in Fig. 3, the bounding edge portion of Fig. 3 beingcomposed of straight portions 2i and 22'connected by suitable curvedportions 23. The respective edges 20 in an assembly including units ofthis character are thus substantially bounded by pairs of parallelplanes. Inplace of the conformation shown in Fig. 3, the edge portionmay be generally circular in outline as shown in Fig. 4, at 20' and intheassembly of units of this character the respective edges 20 arebounded by a cylindrical surface.

The edge portions may also, if desired be made as a segment, as shown inFig. 5, at 20", with a portion of the projecting flange or fin omittedand the remaining portion of the interior space i5 enclosed by a wall 24of substantially uniform thickness.

As has been heretofore indicated, the economizer or heat exchanger ofthe present invention may be assembled by weldingtogether, as by meansof the welds 25, a plurality of the forged units i2, the adjoiningchamfered portions l6 being united by the welding so that the thicknessof the wall at the place of welding 'is not de creased by the welding,as indicated in Fig. 1. To one end unit of the series a connecting tubeIi for connection to the header i0 is welded, the other end of theseries being welded to a return bend II. The other end of the returnbend i3 is also welded to another series of assembled forgings l2 whichare welded together in the same manner, and are connected to anotherconnecting tube II and to another header iii.

The fluid to be heated in the econcmizer is passed in a directiongenerally opposed to that of the flow of the hot gases passing over theexterior surfaces, so that if the hot gases pass downwardly from thetop, the liquid to be heated is introduced at the lowermost header l0,passes successively through one tube loop to the next header i0, and, inthe same manner to the uppermost header i0.

It is frequently found desirable, after instal- 1 lation, andparticularly where the tubes are exposed to radiant heat tovary orchange the i heat transferring capacity and the tube construction of thepresent invention is particularly suitable for this purpose.

' After assembly if it is desired to reduce the heat transferringproperties of the tube construction, a coating of refractory material 28in plastic condition may be applied upon the exterior of the assembly ora portion thereof. A relatively large surface for adherence and supportof the refractory material 26 is provided with the construction of thepresent invention. It is desirable, in some instances, however, to

- lock the refractory material 28 in place and for gases flowing overthe exterior surfaces to liquid to be heated flowing within theinterior. The apparatus of the present invention is, however, equallysuitable for transfer of radiant heat, or for transfer in the oppositeor outward direction through the walls of the heat exchanger, so thatheat may be transferred from a hot liquid passing' within the interiorto a cooler gas passing over the outer surface.

I claim:

1. A heat exchanger comprising an assembly of similar units united endto end by welds, each unit having an interior fluid contact passagearranged in alinement with similar passages in the adjoining units, eachof said units having an outer gas contact face, said outer faces eachcomprising a plurality of curved surfaces meeting similar curvedsurfaces of adjoining units at the ends of the unit, said curvedsurfaces extending outwardly from their ends and towards each other toprovide an outwardly extending flange,

vtinuous curved surfaces.

said curved surfaces terminating in an outer edge distant from theinterior passage, and refractory material disposed in spaces defined bysa'i-Elcon- 2. A heat exchanger. having a plurality of similar unitsassembled in series to form a tubular section having an interior fluidcontact passage arranged in alinement with similar passages in theadjoining units, each unit including a forged single body of metalhaving an outer gas contact face, said outer gas contact face includinga plurality of curved surfaces extending from the 1 flanges, andrefractory locking spaces formed insaid curved surfaces.

JOSIAH H. ROHRER. 20

